1. Field of the Invention
The present invention relates data storage devices, or disk drives, of the type that receive a removable disk cartridge. More particularly, the present invention relates to a read/write protect method for inhibiting unauthorized and/or inadvertent reading from, and writing to, a storage medium within a disk cartridge.
2. Description of the Prior Art
Removable disk cartridges for storing digital electronic information typically comprise an outer casing or shell that houses a rotatable storage medium, or disk, upon which electronic information can be stored. The cartridge shell often comprises upper and lower halves that are joined together to house the disk. The disk is mounted on a hub that rotates freely within the cartridge. When the cartridge is inserted into a disk drive, a spindle motor in the drive engages with the disk hub in order to rotate the disk within the cartridge. The outer shell of the cartridge typically has some form of opening near its forward edge to provide the read/write heads of the drive with access to the recording surfaces of the disk. A shutter or door mechanism is often provided to cover the opening when the cartridge is not in use to prevent dust or other contaminants from entering the cartridge and settling on the recording surface of the disk.
Conventional 3.5xe2x80x3 floppy disks have a mechanical slider mounted in a corner of the cartridge housing that can be moved from one position to another to indicate whether the floppy disk is, or is not, write-protected. An optical or mechanical switch in a floppy disk drive detects the position of the mechanical slider on the cartridge to determine whether the cartridge is write-protected. If so, the disk drive inhibits writing of information to the storage medium within the floppy disk cartridge. Unfortunately, the mechanical slider on the disk cartridge and the associated mechanical or optical switches in the disk drive increase the costs of the cartridge and drive. Moreover, there is no way to prevent a user from changing the write-protect status of the cartridge. All a user has to do is change the position of the mechanical slider. Another disadvantage of conventional 3.5xe2x80x3 floppy disks and their associated drives is that there is no simple way to provide read protection in addition to the write protection. Data encryption can be applied to the recorded information, but data encryption techniques are highly complex and costly to implement.
Saldanha et al., U.S. Pat. No. 5,265,230, and Kulakowski et al., U.S. Pat. No. 5,132,954, disclose data storage systems in which at least a portion of a storage medium can be designated as xe2x80x9cread onlyxe2x80x9d by storing a unique data pattern in that portion of the storage medium. However, once a portion of the disk is designated as xe2x80x9cread onlyxe2x80x9d, the xe2x80x9cread onlyxe2x80x9d state is permanent; a user cannot change the state of the xe2x80x9cread onlyxe2x80x9d portion of the storage medium.
Horiguchi, U.S. Pat. No. 5,311,498, discloses a method for password protecting one or more data blocks of an optical card. As Horiguchi describes, optical cards and disks are often used to store important information that may need to be protected from unauthorized reading. According to Horiguchi""s data security method, at the time the important information is recorded on an optical card or disk, a password is stored in any data blocks that are to be protected from unauthorized reading. Only users who know the stored password can read the information in those data blocks. According to Horiguchi, the password protection is permanent. The password protection cannot be removed, even by a user that knows the current password. The current password also cannot be changed. These limitations are appropriate in Horiguchi""s system, because the goal is data security. However, these limitations would be disadvantageous and unworkable in a more flexible read/write protection scheme of the type contemplated herein.
As the foregoing illustrates, there is a need for an improved read/write protection method for inhibiting unauthorized or inadvertent access to the storage medium of a disk cartridge. Preferably, the method would allow both write and read protection to be applied to the storage medium and would allow a user to change the protection mode of the storage medium, if desired. It would also be advantageous if a password could be used, when desired, to prevent unauthorized changes to the protection mode of the storage medium. Preferably, the method would not require additional mechanical or electrical components, nor any physical interaction with the housing of a disk cartridge. The present invention satisfies these needs.
The present invention is directed to a write/read protect method for inhibiting inadvertent and unauthorized writing and reading of information to and from the storage medium of a disk cartridge. The method of the present invention is primarily intended for use in a disk drive of the type that receives a removable disk cartridge, including a conventional 3.5xe2x80x3 floppy disk drive or any other magnetic, optical, magneto-optical or other hard or floppy disk drive that receives removable cartridges. The present invention can also be employed in fixed, or rigid type hard drives.
According to the present invention, a first predetermined location is provided on a storage medium for writing, or storing, a code indicative of, or having a value indicative of, a protection mode of the storage medium. A second predetermined location may also be provided on the storage medium for storing, if desired, a password associated with the code. Possible protection modes include, but are not limited to, a protection mode wherein writing of information to the storage medium is inhibited, a protection mode wherein writing and reading of information to and from the storage medium are not inhibited, and a protection mode wherein both writing and reading of information to and from the storage medium are inhibited. Essentially, each protection mode specifies one of a number of different ways in which access to the storage medium may be inhibited. Whenever access to the storage medium is attempted in a manner that is inhibited by the protection mode of the storage medium, the disk drive preferably will report an error.
Further according to the present invention, a current, or first protection mode indicated by a first code stored in the first predetermined location on the storage medium is changed by (a) receiving a command to change the protection mode of the storage medium from the first protection mode to a second protection mode; and, in response to the command, (c) writing in the first predetermined location on the storage medium, in place of the first code, a second code indicative of the second protection mode.
A password can be written to the second predetermined location on the storage medium in connection with certain protection modes. In such a case, a command to change the protection mode of the storage medium will only be executed if a password received with the command matches the password written in the second predetermined location on said storage medium.
According to another aspect of the present invention, the method may further comprise the steps of (i) reading a first, or initial code written in the first predetermined location on the storage medium upon insertion of the storage medium into the disk drive; (ii) determining from the first code the first protection mode of said storage medium; and (iii) setting at least one flag to indicate the first protection mode of the storage medium. The method of the present invention may still further comprise the steps of (i) receiving a command to temporarily by-pass the protection mode indicated by the code written in the predetermined location on the storage medium; and, in response thereto, (ii) resetting the aforementioned flag(s) to a state that indicates that access to the storage medium is not inhibited. In this mode of operation, a disk drive can access the storage medium in a manner that would otherwise be inhibited by the protection mode indicated by the code on the storage medium, but without having to overwrite that code.
A disk cartridge according to the present invention comprises a storage medium having a plurality of concentric tracks to and from which information may be written and read. The storage medium has written, in a first predetermined location thereon, a code that indicates a protection mode of said storage medium, and has written, in a second predetermined location thereon, a password associated with said code. A disk drive cannot write another code in place of the code written in said first predetermined location unless a password received by the disk drive matches the password written in said second predetermined location. Preferably, the first and second predetermined locations are duplicated at a plurality of positions on said storage medium and on opposite surfaces of said storage medium. Preferably, the first and second predetermined locations are not accessible by a user""s host computer. Only a disk drive according to the present invention can access those locations. The storage medium may comprise any form of rewritable storage media, including, but not limited to magnetic storage media, rewritable optical media and magneto-optical media.
The foregoing and other objects, features and advantages of the invention will become evident hereinafter.